The present invention relates to networks, especially wireless networks communicating between single devices. In particular the present invention relates to network topologies where devices communicate over slotted point-to-point links. More particularly the present invention relates to networks where one device can be connected to multiple other devices, wherein the one device can only communicate with one other device at a time.
Conventional networks, for example a network of microprocessor controlled devices such as computer, printers, modems etc. have relied upon physical wire connections between the devices in the network. Due to the physical nature of the connection required, conventional networks are generally perceived to be fairly rigid in nature. For example, in order to add an additional device into the network, the additional device must be physically connected to the network, and the network server may have to be informed that the additional device has been connected.
Recently however, it has been observed an emerge of wireless networks, in which the network connections are provided, typically by a wireless radio link. One of these networks is described in the various Bluetooth standards (see e.g. http://www.bluetooth.com). Those skilled in the art will appreciate that other wireless networks also exist, and reference herein to Bluetooth is not intended to be limited hereto.
Bluetooth wireless technology allows users to make effortless, wireless and instant connections between various communication devices, such as mobile phones, computers, printers etc. Bluetooth technology provides for a short-range wireless connectivity and supports both point-to-point and point-to-multipoint connections. Currently, up to seven active ‘slave’ devices can communicate with a ‘master’ device, to form a ‘piconet’. Several of these ‘piconets’ can be established and linked together in ad hoc ‘scattemets’, to allow communication among continually flexible configurations.
Due to the wireless nature of the piconet and the scattemet, and to minimise the expense, most of the wireless network devices comprise only one data-transceiver. Therefore the network devices are only capable of communicating with one other network device at a time. Within a piconet with only one master and up to 7 active slaves no special scheduling process has to be used to execute a nearly optimised data transfer. This is due to the fact that the master usually is the device having most computing power, and the slaves usually are peripheral applications for the master device. In this topology the overall communication performance is optimised, when the communication of the master is optimised. At the level of scatternets, the overall communication performance is depending on other parameters. In a scattemet one network device is not fixed with its role to be master or slave, but can be master to some of its links and simultaneously be slave to some other of its links. Therefore an arbitrary or even distribution of priorities or transmission times can always be expected to be sub-optimal.
Prior solutions concerning connections between piconets, such as WO 99/14898 regarding ‘Contemporaneous connectivity to multiple piconets’ have been based on the utilisation of a specified Bluetooth low-power modes and negotiated time periods and were therefore bound to act within certain corresponding limits, e.g. communication overhead resulting from parameter negotiation. In addition, a periodic behaviour was assumed, thereby restricting the adaptivity to varying traffic loads and topologies to a minimum.
One of the problems with the creation of slotted networks is to optimise the overall communication performance.
Another problem with the creation of slotted networks is the fact that the network devices are movable and so the traffic load on the links changes with the location of each network device.
Another problem related to slotted networks is to share the available communication time in a fair manner.